If you went for a whole bunch of very famous people at once, I do think many people would start believing it's one of the following:

(a) God

(b) Their own government

(c) Some super-secret organization that is somehow far more technologically advanced than any governments, and which likely has infiltrated those governments

(d) Aliens

Basically, if you make it very, very obvious (like, say, killing every famous politician you can think of on the same day), people WILL believe in weird things. The world you and I believe in is already bursting full of people who believe in magic. They're just very particular about which magic they believe in.